"Triathletes report being uncoordinated when running after cycling." This study investigated a) the influence of the bike-run transition on neuromuscular coordination of running (does cycling have a direct effect on running?), b) the effect of altered neuromuscular coordination on run economy (RE - steady-state V02), c) the association between a history of exercise-related leg pain and neuromuscular coordination, and d) the role of fatigue in coordination changes in highly trained triathletes (N = 27). 3-D pelvic and lower limb kinematics and leg muscle recruitment were compared between a control-run with no prior exercise and a 30-minute transition-run preceded by only 20 minutes of cycling (run vs. cycle-run).

Kinematics in the control and transition-runs were no different. Muscle recruitment was different in 5 of 17 Ss without a history of injury. Altered muscle recruitment during the transition-run was more like the recruitment used during cycling. Altered muscle recruitment was associated with a slight increase in VO2. Muscle recruitment was altered in 7 of 10 Ss with a history of exercise-related leg pain. Altered muscle recruitment was not associated with indicators of fatigue from myoelectric and force data.

Implication. Short periods of cycling have no direct effect on running kinematics or muscle activity in most highly trained triathletes. However, running muscle activity is influenced by cycling in a proportion of highly trained triathletes. This influence is not related to altered kinematics or fatigue, but instead appeared to be a direct effect of cycling on motor commands for running. The altered muscle recruitment was associated with reduced running economy and 2.4 times greater likelihood of a history of exercise-related leg pain.